Carbon monoxide
[CAS# 630-08-0]

Identification

• Classification: Inorganic chemical industry >> Industrial gases such as hydrogen, nitrogen and oxygen
• Name: Carbon monoxide
• Molecular Formula: CO
• Molecular Weight: 28.01
• CAS Registry Number: 630-08-0
• EC Number: 211-128-3
• SMILES: [C-]#[O+]

Properties

• Melting point: -205 $degree$C (Expl.)
• Boiling point: -191.5 $degree$C (Expl.)
• Solubility: soluble in ethanol, benzene, acetic acid (Expl.)

Safety Data

• Hazard Symbols: GHS02;GHS04;GHS06;GHS08 Danger
• Risk Statements: H220-H360D-H331-H372
• Safety Statements: S53;S45

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Specific target organ toxicity - repeated exposure	STOT RE	1	H372
Acute toxicity	Acute Tox.	3	H331
Reproductive toxicity	Repr.	1A	H360
Gases under pressure (compressed)	Press. Gas (Comp.)		H280
Flammable gases	Flam. Gas	1	H220
Reproductive toxicity	Repr.	1A	H360D
Acute toxicity	Acute Tox.	2	H330
Reproductive toxicity	Repr.	1A	H360D

• Transport Information: UN 1016 - class 2 - Carbon monoxide, compressed

Discovery and Applications

Carbon monoxide is a colorless, odorless, and tasteless gas consisting of one carbon atom covalently bonded to one oxygen atom. It is a simple diatomic molecule with a triple bond between carbon and oxygen, including one sigma bond and two pi bonds, which gives it high bond energy and chemical stability. Carbon monoxide is widely recognized for its role as a toxic gas, but it also has significant industrial applications as a reagent and building block in chemical synthesis.

The gas is typically produced by incomplete combustion of carbon-containing fuels, such as coal, natural gas, gasoline, and biomass, where insufficient oxygen prevents full oxidation to carbon dioxide. Carbon monoxide can also be generated in controlled industrial processes, such as the reaction of carbon dioxide with heated carbon or by water–gas shift reactions in the production of synthesis gas. Due to its high affinity for hemoglobin, carbon monoxide is highly toxic to humans and animals, causing interference with oxygen transport in the blood.

Industrial applications of carbon monoxide are extensive due to its ability to act as a reducing agent and a source of carbon in chemical synthesis. It is a key component of synthesis gas (syngas), which is a mixture of hydrogen and carbon monoxide used to produce methanol, acetic acid, and other chemicals. Carbon monoxide also plays a critical role in hydroformylation reactions, where it reacts with alkenes and hydrogen to form aldehydes, a process widely used in the production of plasticizers, detergents, and fragrances.

In metallurgy, carbon monoxide is used as a reducing agent to extract metals from their ores. For example, in the production of iron from iron ore in blast furnaces, carbon monoxide reduces iron oxides to metallic iron while being oxidized to carbon dioxide. Its reducing properties are also utilized in the production of other metals, such as tungsten and molybdenum, from their oxides.

Despite its toxicity, carbon monoxide has been explored for specialized applications in medicine and research. It can act as a signaling molecule in low concentrations, and carbon monoxide–releasing molecules (CORMs) are studied for potential therapeutic effects in modulating inflammation, oxidative stress, and vascular functions. However, strict safety protocols are essential due to the narrow margin between effective and toxic doses.

Overall, carbon monoxide is a simple diatomic molecule with both hazardous and industrially valuable properties. Its strong triple bond, chemical reactivity, and reducing ability make it indispensable in chemical synthesis, metallurgy, and energy production, while its toxicity requires careful handling and monitoring in both industrial and experimental settings.

References

2025. Tracing CO2 emission characteristics in Central China based on the simultaneous measurements of atmospheric CO2, CO and δ13C. Journal of environmental sciences (China).
DOI: 10.1016/j.jes.2024.09.024

2025. Characterizations of air pollutants at roadside monitoring stations and traffic emission effects: A case study in Tianjin, China. Journal of environmental sciences (China).
DOI: 10.1016/j.jes.2024.09.018

2025. Defect anchored single atomic Tin-nitrogen sites on graphene nanomesh for enhanced CO2 electroreduction to CO. Journal of environmental sciences (China).
DOI: 10.1016/j.jes.2024.06.001